问题
Is there any way I can specify a standard or custom numeric format string to always output the sign, be it +ve or -ve (although what it should do for zero, I\'m not sure!)
回答1:
Yes, you can. There is conditional formatting. See Conditional formatting in MSDN
eg:
string MyString = number.ToString("+0;-#");
Where each section separated by a semicolon represents positive and negative numbers
or:
string MyString = number.ToString("+#;-#;0");
if you don't want the zero to have a plus sign.
回答2:
Beware, when using conditional formatting the negative value doesn't automatically get a sign. You need to do
string MyString = number.ToString("+#;-#;0");
回答3:
You can also use format strings in string.Format(); the format string is separated from the index with a colon (':')
var f = string.Format("{0}, Force sign {0:+#;-#;+0}, No sign for zero {0:+#;-#;0}", number);
For number { +1, -1, 0 } this gives:
1, Force sign +1, No sign for zero +1
-1, Force sign -1, No sign for zero -1
0, Force sign +0, No sign for zero 0
You can also use an interpolated string instead of string.Format to obtain the same result:
var f = $"{number}, Force sign {number:+#;-#;+0}, No sign for zero {number:+#;-#;0}";
回答4:
Contrary to the other answers it seems that if you want to get +1, -1, +0 (for arguments 1, -1, 0) you need to use the format:
String.Format("{0:+#;-#;+0}", 0)); // output: +0
or
String.Format("{0:+0;-#}", 0)); // output: +0
If you use just +#;-# it will display just + (not +0) for 0.
The "#" Custom Specifier (at https://msdn.microsoft.com/en-us/library/0c899ak8.aspx)
Note that this specifier never displays a zero that is not a significant digit, even if zero is the only digit in the string. It will display zero only if it is a significant digit in the number that is being displayed.
Also please keep in mind that if you need any decimal precision you need to specify it like that:
String.Format("{0:+0.##;-#.##}", 0)); // output: +0
or, if you wan't zeros to always show up, like that:
String.Format("{0:+0.00;-#.00}", 0)); // output: +0.00
回答5:
For a numeric expression of any type:
+###,###,###,###,###,###,###,###,###,##0.###,###,###,###,###,###,###,###,###,###;-###,###,###,###,###,###,###,###,###,##0.###,###,###,###,###,###,###,###,###,###;0
Use three parts for three cases: positive;negative;zero
Other aspects of the example:
Zero is not signed. You could have it show as anything, such as "zero".
Absolute values less than one have a leading 0 before the decimal point. Adjust to taste.
Number of digits is for the largest and smallest absolute decimal values. Adjust to taste.
Decimal point character is culture-specific. .NET substitutes.
Grouping separators are optional. The character is culture-specific. .NET substitutes. (The positions are also culture-specific but that's only controlled by your format string.) You also use any other character except the special characters for Format (which include , . # 0).
回答6:
I cannot comment so i Do an answer here (nuts reputation system ....)
You can Use number.ToString("+0;-#") very well to Produce the UTC String TimeFormat
Here showed in PowerShell code
"$([System.DateTime]::Now.ToString('HH:mm:ss.fff'))$($([System.TimeZoneInfo]::Local.GetUtcOffset([System.DateTime]::Now).TotalMinutes.ToString('+0;-#')))"
Thank you @gcores https://stackoverflow.com/users/40256/gcores
来源：https://stackoverflow.com/questions/348201/custom-numeric-format-string-to-always-display-the-sign